Bottles are already known that contain a liquid such as a collyrium, and that are provided with dropper systems for dispensing the liquid in the form of drops. Often it is necessary to preserve the liquid from any risk of being contaminated by external agents such as bacteria. Simple means for keeping the liquid sterile consist in using a bottle that contains a single metered quantity only and that is to be discarded after being used for the first time. Unfortunately, the use of disposable bottles is ecologically harmful.
As an alternative to using such a single-dose bottle, it is possible to use a bottle designed to be used a plurality of times, and that can be closed again once a metered quantity has been dispensed, in order to dispense other metered quantities of liquid subsequently. The difficulty that arises when using a multi-dose bottle is how to preserve the stored liquid. Each time a metered quantity of liquid is dispensed, there is a risk that external agents might enter the container, and thereby contaminate the stored liquid. In order to make sure that the liquid is not contaminated, chemical preservatives are generally added to the liquid. Unfortunately, it has been observed that the use of such preservatives can give rise to allergies in certain users, or to undesirable side effects.